Melatonin is a kind of indoleamine and synthesized from L-tryptophan through serotonin mainly in pineal organ. As a melatonin receptor, MT1, MT2 and MT3 are known. A melatonin MT1 receptor inhibits nerve firing in suprachiasmatic nucleus and has a function to induce sleep. It has been known that a melatonin MT1 receptor antagonist has antidepressive activity.
Tyrosine is one kind of natural amino acids, and utilized as an amino acid which constitutes an enzyme and a structural protein in a living body and as a biologically active substance or the raw material compound thereof. For example, it is described in Non-patent Document 1 that m-tyrosine can be used as an herbicide to inhibit root growth of a plant. In addition, a tyrosine derivative is useful as a synthetic intermediate of various useful substances.
If an iodine atom can be introduced in a benzene ring of tyrosine, various compounds which are chemically or pharmaceutically useful can be synthesized from the thus obtained derivative by a functional group transformation reaction or the like, since an iodine atom is more reactive than a general chlorine atom and bromine atom among a halogen atom. For example, a compound which has an iodinated benzene ring can be utilized as a substance of Grignard reaction, Heck reaction and other coupling reaction.
When an iodine atom is introduced in a benzene ring of tyrosine, it is necessary to control the position of the iodine atom to be introduced. For example, it is described in Non-patent Document 2 that an iodine atom is introduced at the para position to the position of a protected phenolic hydroxy group of a benzene compound by reacting iodine with the benzene compound in the presence of silver trifluoroacetate.